Light degradable thermoplastic molding composition based on polyacetals

ABSTRACT

POLYACETALS. I.E. HOMOPOLYMERS OF FORMALDEHYDE OR OF TRIOXANE OR COPOLYMERS OF TRIOXANE WITH MONOFUNCTIONALLY REACTING COMPOUNDS SUCH AS CYCLIC ETHERS OR CYCLIC ACETALS AND POSSIBLY POLYFUNCTIONALLY REACTING COMPOUNDS CAN BE PROTECTED BY ADDITION OF STABILIZERS AGAINST THE ACTION OF HEAT AND OXYGEN. THEY CAN, HOWEVER, BE DEGRADED BY THE ACTION OF ULTRA-VIOLET LIGHT IF THEY CONTAIN LIGHT SENSITIZERS, FOR EXAMPLE ANTHRONE. THE POLYACETALS ARE SUITABLE FOR THE MANUFACTURE OF SHAPED ARTICLES, ESPECIALLY SHEETS.

Patented Sept. 10, 1974 I Claims priority, application Germany, Sept. 16, 1971,

P 21 46 374.1 Int. c1. C08g 1/02 US. Cl. 260-67 FP 7 Claims ABSTRACT OF THE DISCLOSURE Polyacetals, i.e. homopolymers of formaldehyde or of trioxane or copolymers of trioxane with monofunctional- 1y reacting compounds such as cyclic ethers or cyclic acetals and possibly polyfunctionally reacting compounds can be protected by addition of stabilizers against the action of heat and oxygen. They can, however, be degraded by the action of ultra-violet light if they contain light sensitizers, for example anthrone. The polyacetals are suitable for the manufacture of shaped articles, especially sheets.

The present invention relates to a light degradable thermoplastic molding composition based on polyacetals.

It is known that homopolymers of trioxane or of formaldehyde with esterified or etherified terminal groups and copolymers of trioxane and small quantities of cyclic formals or cyclic ethers can be protected against the action of heat, oxygen and light by adding stabilizers. Suitable heat stabilizers are for example polyamides, amides of polybasic carboxylic acids, amidines, hydrazines, ureas and poly(N-vinyl-lactams). As oxidation stabilizers phenols, especially bisphenols, and aromatic amines are used whilst the derivatives of alpha-hydroxybenzophenone and of benzotriazole serve as stabilizers against the action of light. The stabilizers are generally used in total amounts of from 0.1 to 10, preferably 0.5 to by weight calculated on the total mixture.

The products obtained after stabilization are characterized by excellent working properties and durability; the latter property may, however, cause ditficult problems in view of the fight against pollution. Therefore, it is desirable to produce poly(oxymethylenes) with the same good working properties we know already, which are, however, less resistant to the action of ultra-violet light, to which they are exposed when deposited in the open air.

Object of the present invention is a thermoplastic molding composition which degrades in ultra-violet light and substantially consists of a mixture of from (a) 99.9 to 90% by weight of an oxymethylene polymer, and

('b) From 0.1 to by weight of a mixture consisting of 10 to 30% by weight of one of the known heat stabilizers and 90 to 70% by weight of anthrone. Thus the molding composition may contain from 0.07 to 9% of anthrone, based on the total weight of the composition.

As oxymethylene polymers there may be used either homopolymers of formaldehyde or of trioxane or copolymers of trioxane and a cyclic ether or a cyclic formal differing from trioxane or a linear polyacetal; or terpolymers of trioxane, a cyclic ether or a cyclic formal differing from trioxane and a polyfunctionally reacting compound.

The portion of homo-, coor terpolymer of trioxane in the molding composition of the invention is preferably from 99.5 to 95% by weight, whilst the portion made up of the heat stabilizer and anthrone is preferably from 0.5 to 5% by weight. Those molding compositions show particularly good properties which consist of from 99.5 to 98% by weight of a homo-, coor terpolymer and from 0.5 to 2% by weight of a mixture of a stabilizer and a sensitizer.

By homopolymers of formaldehyde or trioxane we mean to include those polymers of which the terminal hydroxy groups have been chemically stabilized against degradation, for example by esterification or etherification.

When using copolymers there are employed as comonomers cyclic ethers and cyclic formals differing from trioxane and of the formula I In this formula x is either an integer of from 1 to 3 and y is zero, or

x is zero, y is an integer of from 1 to 3 and z is 2, or

x is zero, y is 1 and z is an integer of from 3 to 6, preferably 3 or 4.

As cyclic ethers there are suitable above all those containing 3 ring members, for example ethylene oxide, styrene oxide, propylene oxide and epichlorohydrin as well as phenylglycidyl ether.

\As cyclic formals there are suitable mainly cyclic formals of aliphatic or cyclo-aliphatic alpha, omega-diols having from 2 to 8, preferably from 2 to 4 carbon atoms, the carbon chain of which may be interrupted by an oxygen atom at intervals of 2 carbon atoms, e.g. glycol formal (1,3-dioxolane), butanediol formal (1,3-dioxepane) and diglycol formal (1,3,6-trioxocane) as Well as 4-chloromethyl 1,3 dioxolane and hexanediol formal (1,3 dioxonane).

Equally suitable are copolymers of trioxane with linear polyacetals.

By linear polyacetals We mean to include both homoor copolymers of the cyclic acetals as defined above, as well as linear condensates of aliphatic or cyclo-aliphatic alpha,omega-diols with aliphatic aldehydes or thio-aldehydes, preferably formaldehyde. Especially useful are homopolymers of linear formals of aliphatic alpha,omegadiols having from 2 to 8, preferably from 2 to 4 carbon atoms, for example poly(dioxolane) and poly(dioxepane) Cyclic ethers or cyclic formals differing from trioxane or linear polyacetals are employed as comonomers or cocomponents preferably in quantities of from 1 to 5% by weight, calculated on the total amount of components to be polymerized.

When using terpolymers the cyclic ethers or cyclic formals differing from trioxane specified above are employed preferably in quantities of from 0.5 to 2% by weight. Of the polyfunctional compounds generally a quantity of from 0.01 to 5, preferably 0.05 to 2% by weight is used. As polyfunctionally reacting compounds there are employed mainly alkylglycidyl formals, polyglycoldiglycidyl ethers, alkanedioldiglycidyl ethers and bis(alkanetriol)- triformals.

By alkylglycidyl formals we mean to include com pounds of formula II in which R means an aliphatic alkyl radical having Im 10, preferably 1 to 5 carbon atoms. Particularly suitable are alkylglycidyl formals of the above formula in which R represents a linear aliphatic alkyl radical of low molecular weight, e.g. methylglycidyl formal, ethylglycidyl formal, propylglycidyl formal and butylglycidyl formal.

As polyglycoldiglycidyl ethers compounds of formula III are suitable.

phenone (Comparative Example F) or ffiuorenone (Comparative Example G) also cause a quick degradation of the polymer exposed to ultra-violet light, but at the same time damage the other properties so severely that it is impossible to process such a product.

5 in which n represents an integer of from 2 to 5. Particu- BY f f f a cPnslderfible degree larly suitable are polyglycoldiglycidyl ethers of the above P degrildatlon Pltra'vlolet ,hght Wlthout, any 5 formula, wherein n is 2 or 3, for example diethylem} influencing the physical properties and Working properties glycol diglycidyl ether and Lethyleneglycoldiglycidyl 0f the pl'OdllCt. The Values 0f thermostabihty and the amen melt mdICB S are exactly the same as m the case of poly- As alkanedioldiglycidyl ethers compounds of iormula acetal stablhzed 1n the normal f- IV are suitable For the production of the molding composltion of the invention the components are mixed thoroughly with one Iv ET E'7 another in the form of powder or granules at a tempera- 0 0 15 ture of below 100 C., preferably between 15 and 50 C., wherein w is an integer of from 2 to 6, preferably 2 to 4. and the t is Subsequently hmtmgenized. the i Especially suitable is butanedioldiglycidyl ether. The homogempw may .take place m any mlxmg device By bis(alkanetrioI)-triformals we mean to inclue comfor example m Ion Imus calendars or pounds with one linear and two cyclic formals groups, traders, at a temperature above the crystallite melting especially compounds of formula V point of the components, i.e. at a temperature of from 150 to 250 C., preferably from 170 to 200 C. After the v cflr'fHflwm)I O CH O(CHZ) ?E EFH' homogenizing the mixture is comminuted, for example 0 O 0 granulated, rasped or pulverized, when it is still hot or Q already cooled down, i.e. still in the plastic or already I in the solid state. Preferably, the plastic mass is granuwhel'em P and q fepreseflt each of from 3 lated at a temperature of from 170 to 250 C., or it is preferably 3 or 4. Particularly suitable are symmetrical cooled by means f an air or water bath and is than bis(alkanetriol) formals of the above formula, in which p granulatgd. and q are q for f p ur r P On the one hand, the molding composition of the informal and Preferably tljlfol'maL vention can easily be processed, but permits, on the other The homolfolymers P Y of Prioxafle used hand, manufacture of shaped articles with a reduced durafor 8 composmon of the P F ff bility when exposed to ultra-violet light. The molding Obtalned: known manner by catalytlc pcflymenzatlon composition is particularly suitable for the manufacture of the monomer German Auslegeschnft 1,037,705 of packing material, for example sheets, bags and sacks. and German Pat. 1,137,215). The copolymers or terpolymers of trioxane used for the molding composition of the EXAMPLES invention can be equally obtained, in known manner by polymerizing the monomers in the presence of cationic Polymer powder, stabilizer and sensitizer were thoroughcatalysts at temperatures between 0 and 100 C., preferly mixed at room temperature and homogenized in a ably 50 and 90 C. (cf. for example German Auslegesingle screw extruder at 200 C. schrift 1,420,283). As catalysts for this purpose there For measuring the degradation in ultraviolet light may be used protonic acids, e.g. perchloric acid, or Lewis sheets of a thickness of 100 microns were put on an acids, for example boron trifluoride and its complex comaluminum foil. Their brittle time was determined in 21 pounds. The polymerization can take place in bulk, susweathering apparatus (system Casella) of Messrs. Heraeus pension or solution. For the removal of unstable pora an) (See catalogue of Messrs. Quarzlampen Geselltions it is best to subject the copolymers to a partial con- Schaft IIlbH n)- trolled thermal or hydrolytic degradation to the primary In order to judge the working properties the reduced terminal alcohol groups (cf. German Auslegeschriften specific viscosity (RSV), the thremostability AG and melt 1,445,273 and 1,445,294). index i were determined in comparison to products stabil- By usual heat stabilizers we mean to include for exized as usual (Comparative Examples A to E). ample polyamides, amides of polybasic carboxylic acids, The Values of the l'fidllced Specific Viscosity of the P amidines, for example dicyanodiamide, hydrazines, ureas, lymefs were measured in butyl'olactone containing 2% poly(N-vinyl-lactams) and alkaline earth metal salts of y weight of dipheglrlamine at a temperature of 1 saturated or unsaturated carboxylic acids with 10 to 20, and m a concfiml'atlcfn 0f 81100 preferably 12 to 18 carbon atoms, for example the calcium The melt Index 2 was measured In accordance wlth salts f lamic m; or i i i acid DIN53,735 at a temperature of 190 C. and under a load It is surprising that anthrone should be suitable as of sensitizer in the production of poly(oxymethy1enes) d The thermostability was measured by the determination gradable under the influence of ultra-violet light since of the loss of weight occurring in air at a temperature other systems containing carbonyl groups such as benzoof 230 C. in the course of 2 hours.

TABLE 1 (Comparative examples) Brittle Copolymer (percent by Stabilizer (0.197; of a mixture Value fr RSV AG time Number weight) containing) Sensitizer (gJlO min.) (dL/g.) (percent) (hours) A Trloxane (98), ethylene oxide 1 part DOD, 5 parts MBP- 9. 5 0. 79 2. 5 400 B 21 W lpart calcium ricinioleate,5 9.2 0.75 2.3 440 parts BDE. 0.: Formaldehyde hoiopolymer fin r 10.1 0.80 4.3 380 1).- Trioxane (97), dioxolane (3)- do 9. 8 0.72 2. 7 410 E Trioxane (97, ethylene do 7. 4 1. 9 400 oxide (2), butane-dioldiglycidyl ether (0.05 F Trioxane (97), dioxolane (3)..- Calcium ricinoleate :.r: 0.5% benzophenone 20.2 0.3 41.0 140 G I do (in 0.5% fiuorenoue 15.3 0. 4 28. 6 H dn dn 12.3 0.8 35.0 311 TABLE 2 (Examples according to the invention) Brittle Copolymer (percent Stabilizer (0.1% 01a Value 1': RSV AG time No. by weight) mixture containing) sensltizer (g./10 min.) (d1. /g.) (percent) (hours) 1 Trioxgnrz2g98), ethylene Calcium ricinoleate. 0.5% anthrone 9. 8 0. 75 1. 9 80 on e 2 Formaldehyde homopolymer do .d 10.9 0.80 4. 6 70 3 Trioxane (97), dioxolane (3) (10... 9.3 0.72 2.9 60 DC 9. 4 0. 8 3. 0 60 Trioxane (97, 95), ethylene Calcium ricinoleate.. ..d0 8.0 2.3 75

oxide (2), butane-dioldiglycidyl ether (0.05).

N 0TE.-BD E fl,x-bis[4-hydroxy-3,5-di-tert.butylphenyll-dipropionic acid-hexane-diol-(1,6) ester; D CD =dicyanodiarnide;

MB P =2,2-methy1ene-bis (i-methyl-o-tert.butylphenol) What is claimed is:

1. A thermoplastic molding composition based on polyacetals, essentially consisting of a mixture of (a) from 99.9 to 90% by weight of an oxymethylene polymer, and

(b) from 0.1 to 10% by weight of a mixture of from 10 to 30% by weight of a conventional heat stabilizer and from 90 to 70% by weight of anthrone.

2. A molding composition according to claim 1 containing from 0.5 to 5% by weight of the mixture of heat stabilizer and anthrone.

3. A molding composition according to claim 1 wherein the oxymethylene polymer is a copolymer of trioxane and a compound of the formula in which x represents either an integer of from 1 to 3 and y is zero, or in which x is zero, y is an integer of from 1 to 3 and z is 2, or in which x is zero, y is 1 and z is an integer of from 3 to 6 4. A molding composition according to claim 1 wherein the oxymethylene polymer is a homopolymer of formaldehyde or trioxane.

5. A molding composition according to claim 1 wherein the heat stabilizer is a polyamide, an amide of a polybasic carboxylic acid, an amidine, a hydrazine, a urea derivative, a poly(N-vinyllactam) or an alkaline earth metal salt of a carboxylic acid or of a mixture of at least 2 of the said compounds.

6. A process for the production of a thermoplastic molding degradable in ultra-violet light, wherein 99.9 to 90 parts by weight of an oxymethylene polymer are mixed with 0.1 to 10 parts by weight of a mixture of from 10 to parts by weight of a heat stabilizer and from 90 to parts by weight of a light sensitizer which is anthrone, as a light sensitizer.

7. A thermoplastic molding composition consisting essentially of an oxymethylene polymer containing from 0.07 to 9% by weight of the composition of anthrone as a light sensitizer.

References Cited UNITED STATES PATENTS 11/1965 Potts, Jr. et al. 260DIG. 43 8/1972 Heinz et al. 26045.9 P 

